Sometimes called "the father of cloning", German scientist Hans Spemann conducted primitive cloning experiments and studied how embryo cells develop. In his earliest experiments, he split the cells of a two-celled salamander embryo into two parts, successfully producing two larvae. This disproved the then-accepted theory that cell division entails the loss of genetic information. Decades before it became technically possible he proposed using the nuclear transfer method to clone entire organisms.

Using micro-surgery techniques, he operated on fertilized animal eggs which were smaller than pinheads. His experiments showed that when an embryo is transplanted to a different region of an animal, it causes the surrounding tissue to develop abnormally, "as if it were the bastard of some primitive miscegenation." Called "the organizer effect", this research won Spemann the 1935 Nobel Prize for Medicine.